Low-visibility aviation operations may be enhanced by electronic visual aids, such as Enhanced Vision Systems (EVS) and Synthetic Vision Systems (SVS) configured for operation in infrared (IR) or radio frequency (RF) spectral bands as well as the visible band. EVS, SVS, and other imaging streams may be simultaneously piped into the cockpit and combined into a single Combined Vision System (CVS) that obviates the need for manual selection of the most useful stream by the pilot or crew as well as the need for the pilot or crew to evaluate the contributions of each individual stream.
A single, cohesive imaging stream incorporating multiple varied sensor sources holds great potential benefit to the situational awareness of the pilot or crew. However, individual imaging streams play specific roles depending on the current flight segment (approach, landing, taxi, takeoff) and the use of particular sources may be mandated or precluded by regulations. For example, FAA operating rules may preclude the use of SVS below a certain altitude AGL; further, EVS may only be used as a visual means of positioning and navigation provided the pilot or crew are able to detect via EVS specific, predetermined visual references indicative of the airfield such as approach lighting or runway markings.